Question: $ { \left[\begin{array}{r}{-1} \\ {2} \\ {3}\end{array}\right]-\left[\begin{array}{r}{-1} \\ {2} \\ {1}\end{array}\right] = {?} } $
Explanation: To find the difference of two matrices, subtract the corresponding items between each matrix. ${\left[\begin{array}{r}{-1}-{-1} \\ {2}-{2} \\ {3}-{1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{r}{0} \\ {0} \\ {2}\end{array}\right]}$